1. Technical Field
Systems and methods for controlling an internal combustion engine to monitor valve deactivation using exhaust pressure.
2. Background Art
Fuel economy for a multi-cylinder internal combustion engine can be improved by deactivating some of the engine cylinders under certain operating conditions. Reducing the number of operating cylinders reduces the effective displacement of the engine such that it is sometimes referred to as a variable displacement engine. Depending upon the particular configuration of the variable displacement engine, one or more cylinders may be selectively deactivated to improve fuel economy under light load conditions, for example. In some engine configurations, a group of cylinders, which may be an entire bank of cylinders, is selectively deactivated. Cylinder deactivation may include deactivation of intake valves, exhaust valves, or both depending upon the particular application and engine technology. Various techniques have been developed for activating and deactivating intake and/or exhaust valves that rely on mechanical, hydraulic, electric/electronic or combination devices to implement valve deactivation in response to a command signal from an engine controller.
A number of strategies have been used to monitor operation of valve deactivation systems. One strategy analyzes the period between intake pressure pulses measured by a manifold absolute pressure (MAP) sensor to monitor operation of an intake valve deactivation system. However, this strategy is not believed to provide a reliable indicator for monitoring exhaust valve deactivation. One technique for monitoring operation of exhaust valve deactivation includes monitoring a knock sensor.